(1960s)

• The earliest climate models.
• They treat Earth like a single box system, calculating surface temperature by balancing incoming solar radiation vs outgoing infrared radiation.
• Essentially, they answer: “How warm should Earth be if X amount of energy comes in and Y amount goes out?”

• Very simple; first to link CO₂ emissions with global warming.
• Computationally inexpensive.

• Oversimplified — ignores atmosphere, oceans, and circulation.
• Cannot simulate rainfall, winds, or regional climate.

(1960s–70s)

• Introduced the vertical structure of the atmosphere.
• They divide the atmosphere into layers and simulate how radiation (solar + infrared) and convection move heat upward and downward.
• Show how greenhouse gases trap heat and alter temperatures at different heights.

• Capture greenhouse effect more realistically;
• Explain vertical temperature profiles;
• Useful for studying stratospheric cooling.

• Still ignore oceans and global circulation;
• Cannot project regional variations or weather patterns.

(1970s onwards)

• The first 3D models of Earth’s climate.
• Divide the planet into grid cells (100–250 km), each with equations for atmosphere, oceans, ice, and land.
• Simulate winds, currents, rainfall, temperature, and pressure by solving physical equations of motion, energy, and mass.

• Comprehensive representation of climate;
• Simulate monsoon, El Niño, ocean currents; reproduce past climate trends.

• Very resource-intensive; grid too coarse to capture local detail (cities, villages);
• Uncertainty in clouds and aerosols.

(1990s–present)

• Advanced GCMs that integrate biogeochemical cycles (carbon cycle, vegetation, ocean chemistry, aerosols, land-use changes).
• Show how human activities (deforestation, fossil fuels, pollution) interact with natural systems, feedback loops, and long-term climate.

• Holistic view of climate–biosphere interactions;
• Essential for IPCC reports and policy projections.

• Extremely complex;
• Uncertainties in carbon feedbacks, aerosols, and long-term ecological processes.

(1990s–present)

• High-resolution versions of GCMs, zoomed into specific regions (25–50 km grids).
• Use downscaling techniques to provide localised forecasts of rainfall, temperature, droughts, and monsoons.

• Useful for city- or country-level policy (flood risk, agriculture, urban heat);
• Capture Indian monsoon and Himalayan glaciers better.

• Dependent on GCM input;
• Projections limited to chosen region;
• Computationally intensive.

I. Peninsular India will most likely suffer from flooding, tropical cyclones and droughts.

II. The survival of animals including humans will be affected as shedding of their body heat through perspiration becomes difficult.

Select the correct answer using the code given below:

(a) I only      (b) II only      (c) Both I and II      (d) Neither I nor II